Welding system



y 1952 c. E. sum-1 2,597,959

WELDING SYSTEM Original Filed Dec. 16, 1943 zsnm'rs-suEEw 1 May 27, 1952c, $M|TH 2,597,959

WELDING SYSTEM Original Filed Dec. 16, 1945 2 Sl-IEETS-SHEET 2 E13. zf'a Patented May 27, 1952 WELDING SYSTEM Clyde E. Smith, Warren, Ohio,assignor to The Taylor-Winfield Corporation, Warren, Ohio, a

corporation of Ohio Original application December 16, 1943,'Serial No.514,491, now Patent No. 2,477,211, dated July 26, 1949. Divided and thisapplication July 18, 1949, Serial No. 105,380

6 Claims. 1

The present application is a division of application Serial No. 514,491filed December 16, 1943, now U. S. Patent No. 2,477,211, issued July 26,1949.

This invention relates to electric resistance welding systems and moreparticularly to improved methods, circuits, and devices for translatingthe electrical energy to the Weld and for controlling the operation ofthe translating means employed. A primary object of the invention is theprovision of an improved system for furnishing'direct current energy tothe weld from an alternating current source. The application of suchcurrent, particularly of large values and short durations of flow, hasbeen found advantageous for certain welding operations principally inthe field of alloys and while it has heretofore been proposed to employsystems utilizing a welding transformer and a rectifier interposedbetween the output of the transformer and the welding load such systemshave not been amenable to proper or efiicient control. It isaccordinglya more specific object of the invention to provide in awelding system having means to furnish a uni-directional welding currentfrom an'alternating current source an improved arrangement forcontrolling the flow of welding energy. While the employment of therectifier and the consequent furnishing of the uni-directional currentto the welding machine proper lessens welding inconsistency which is dueto the inductive effect of the adjacent welding current carrying partsof the machine and of the variable position of the work in the throat ofthe machine variations in line voltage continue to lend inconsistency tothe welding results and another object of the invention is to eliminatethis inconsistency entirely in a welding system of the kind involved.

A further object of the invention is the provision of improved,simplified and more economic circuit arrangements for controlling thehow of and, in addition, the usual heat control to pro vide anadjustment to compensate for variations in the dimensions or characterof the stock and in the ,quality of the weld being produced. Inthe'conventional three-phase three-wire supply circuit aneffectivecontrol of more than ample range may be provided by controlling in amodulating manner the conduction in but one of the conductors whilesimple open or closed contactors are employed in the other twoconductors.

A still further object of the invention is the provision of an improvedcircuit arrangement for modulating the flow of energy from a supplycircuit to a load circuit in accordance with variations in voltage inthe supply circuit.

Yet another object of the invention is the provision of improved andmaterially simplified circuit arrangements for modulating the flow ofenergy froma polyphase source of electrical power to a Welding load inaccordance with variations in the voltage of the source.

Other objects of the invention include the provision of improved circuitarrangements for actuating a welding pressure changing device in timedsequence following the initiation of the flow of welding current and forutilizing such, control in a direct current welding system.

Other objects and advantages of the invention will become apparent uponconsideration of the following detailed specification and theaccompanying drawing wherein there is specifically disclosed a preferredembodiment of the invention.

The single figure of the drawing, on two sheets, is a schematic diagramof a spot Welding system constructed in accordance with the principlesof the invention.

Referring'to the drawing, Ll, L2 and L3 will be the line conductors of aconventional threephase source of alternating current whil referencenumeral H indicates a welding transformer, the primary of which isconnected in star and adapted to be connected to the line conductors LI,L2, L3 while the secondary of which is connected in delta for furnishinglow voltage electrical power to the full wave welding rectifiers l2.Rectifiers l2 are of the dry plate type having suificient surge capacityto handle the heavy currents normally employed in welding operationsand, as shown, the output thereof is connected to fixed electrode l3 andto the movable electrode M of the welding machine. While I have shownthe electrodes as being of stud form, it should be apparent that theinvention is equally applicable to welding systems generally includingseam welders employing wheel electrodes.

Conductors LI and L2 are arranged to be connected, in the preferred andillustrated embodiment of the invention, to the primary winding of thetransformer H through the contactors I5 and I6 of a relay I! having anenergizing .0011 IS. The third conductor L3 of the source is connectedto the primary of transformer through the valves |9 and 26, connected ininverse parallel, and preferably of the ignitron type. As such, valves[9 and each has an anode, a mercury pool cathode and an ignitionelectrode arranged to be energized at controlled times during the halfcycles of the current source. For this purpose, a discharge device 2| ofthe gas filled type is connected across the anode and ignition electrodeof the valve I9 and a. similar device 22 is provided for the valve 20.Normal negative grid bias suflicient to hold the device 2|non-conducting is furnished by a rectifier 23 deriving energy from acontrol current line 24 through a transformer 25. Line 24 may beenergized through a transformer 26 on the conductors L2, L3. The outputof rectifier 23 develops a voltage across the resistor 21 which is inthe grid biasing circuit for the device 2|, the circuit including thesecondary 28 of the grid transformer 29. Similarly normal negative gridbias for device 22 is developed across a resistor 39 by a rectifier 3|also deriving energy from transformer 25. Resistor 39 is in the gridcircuit for device 22, which circuit also includes the secondary winding32 of the grid transformer 33.

The primary 34 of transformer 29 is in a circuit which may be tracedfrom an end terminal 35 of a center-tapped secondary winding of thetransformer 25 through conductor 36, winding 34,

conductor 31, anode-cathode of a grid controlled gas discharge device38, potentiometer 39, contactor of a relay 4| having an energizing coil42, and conductor 43 to the center tap 45 of said secondary winding.former 33 is in a circuit which may be traced from the other endterminal 46 of said secondary winding through conductor 41, winding 44,conductor 48, anode-cathode of a grid controlled gas discharge device49, and then through resistor 39 and contactor 40 to the center tap 45.Thus by the initiation 'of conduction in the tubes 38 and 49 atpredetermined times during the positive or negative half cycles ofpotential appearing across the valves |9 and 20 the grid transformers 29and 33 will be impulsed to permit the valves I9 and 29 to translatepredetermined portions of the respective half cycles of energy as willbe well understood,

To provide for a base or heat control through the devices 38 and 49 ofthe quantity of energy transmitted by the valves l9 and 20 I provide aphase shifting circuit 50 the input of which is connected to acenter-tapped winding 5| of a transformer 52, the primary of which isconnected to the control current line 24 and the output of circuit 50 isimpressed on the primary windings 53 and 54 of grid transformers 55 and56, respectively. The secondary of transformer 55, indicated byreference numeral 51, is in the grid circuit of the tube 38 while thesecondary 58 of the transformer 56 is in the grid circuit of, the tube49. Thus conduction in tubes 38 and 49 is initiated during therespective half cycles at times determined by the phase deviationeffected by the adjustment of the circuit 59 and in this manner a basiccontrol or. adjustment of the total energy furnished is attained.

To provide compensation for voltage fluctuation in the supply circuitwhereby a predetermined constant current is furnished the weldirrespective of variations in the line voltage I introduce in the gridbiasing potentials furnished the control devices 38 ant-1 49 a directcurrent component which varies in accordance with line The primary 44 oftransvoltage conditions. For this purpose a rectifier 59 deriving energyfrom transformer 52 is employed to develop a constant referencepotential across a resistor 69 and this resistor 60 is placed in thegrid biasing circuits of the devices 38 and 49 and also in series withthese circuits is a resistor 6| the effect of which will be explainedbelow. Such circuits may readily be traced from the cathodes of thedevices 38 and 49 through conductor 62, resistor 60, conductor 63,resistor 6|, conductor 64, and thence through windings 51 and 58 to thegrids of tubes 38 and 49, respectively. Means is provided to developacross resistor 6| a potential variable in accordance with variations inline voltage and in opposition to the potential developed acrossresistor 60. For this purpose a rectifier deriving energy from line 24through transformer VRT of the voltage regulating type is provided todevelop a uniform potential across a resistor 66, a filter 61 beingemployed to smooth out the ripples in the output. Resistance 66 isprovided with a sliding tap 68 which is connected to the grid end ofresistor 6| by means of the conductor 69. Also connected across theoutput of rectifier 65 and filter 6! is the anode-cathode of agrid-controlled space discharge device 79 and a resistance 1| in series.The latter is provided with an adjustable tap 12 which is connected tothe cathode end of resistor 6| by means of conductor 13. The currentflowing in tube 10 determines the potential at tap l2 and consequentlythe potential at resistor 6|. As the tube 10 draws more current thevoltage at 6| is raised thus driving the direct current component of thegrid bias impressed on the tubes 38 and 49 more positive, forcing themto conduct earlier during the half cycles of the voltage wave.

Conduction in tube 10 is controlled in accordance with the voltage inthe current supply line (L2, L3 in the embodiment illustrated) by meansnow to be described. Connected across the lines L2, L3 throughtransformer 26 and line 24 is the primary winding 15 of a transformer"I6 the secondary ll of which feeds a full wave rectifier 18 which ispreferably of the dry plate type and the output of which is impressedacross a relatively small capacitor 19 and a parallel resistance 80 of apotentiometer. The negative end of resistance 80 is connected to thecathode of tube 10 through resistor while the movable tap of theresistance 60 is connected to the control grid of the tube 10 throughthe usual grid resistor 8|. Thus as the voltage drops in the conductorsL2, L3 the output of rectifier 78 is diminished as is also the potentialdeveloped across resistance 80 and therefore the positive bias on tube10 is lowered causing it to conduct less current the effect of which isto cause earlier conduction in the control devices 38 and 49 asexplained above. While I have shown the line voltage determining means(l886) as being responsive only to the voltage of the phase carried byconductors L2, L3, it should be apparent that the full wave threephaserectifier 13 may equally as well be powered by all the phases if it isdesired to do so.

The improved pressure changing valve solenoid actuating circuit of theinvention will now be de scribed. This circuit consists essentially of asolenoid energizing circuit and a control circuit to initiate the fiowof energy in the energizing circuit at an accurately timed intervalfollowing the establishment of a reference condition which in thepresent case is the initiation of fiowof current through the weld.Reference numeral 83indicates a floating double bellows interposed intheline of drive between the primary actuatingcylinder 84 and the movableelectrode I4 of the: welding machine. Assembly 83 having an exhaustvalve85 operated by solenoid 88 may be ofthetype specifically disclosed andclaimed in co-pending application Serial No. 482,630 of M. A. SeeloffandC. E. Smith, now U. S. Patent No. 2,363,753. To perform a weldingoperation a valve 81 which is normally automatically actuated byappropriate sequencing circuits is provided to admit fluid pressure tothe upper end of. cylinder 84 to effect downward movement of theassembly 83 and electrode I4. A switch 88 forms a part of assembly 83and, as explained more in detail in said co-pending application, thisswitch closes upon yielding of the assembly 83.

Solenoid 86 is arranged to be energizedby discharge. of a capacitor 89effected by conduction in a gridcontrolled gas discharge device 98, thedischarge. circuit being traceable from the positive, terminal ofcapacitor 89 through conductor 9|, contactor 92 of a relay 93 having anactuating coil 94, conductor 95, contactor 98 of relay 93, conductor 91,coil 80, conductor 98, tube 90, and conductor 99 to the negativeterminal capacitor. Capacitor 89 is arranged to be charged from controlcurrent line 24 through transformer I80 and rectifier IOI of thecontrolled gaseous type and to control the potential to which capacitor89 is charged a potentiometer has its resistance I02 connected acrossthe capacitor and a movable tap thereof connected to the control grid ofrec-' tifier I III through conductor I 03, the grid end portion ofpotentiometer I04, conductor I85, and grid resistor I08. A constantbiasing potential is developed across the resistance element ofpotentiometer I04 by a rectifier I! deriving energy from line 24 through.a transformer I08. The polarities of the potentials are as indicated onthe drawing and it should be apparent that as the potential acrossresistance I82 rises to a predetermined adjusted value conduction inrectifier IOI will be interrupted and remain interrupted upon themomentary opening of contactor I09 placed in the primary circuit oftransformer I00. Contactor I09 is arranged to be opened momentarily bya-coil IIO which is energized during flow of weldingcurrent by means ofthe conductors III and H2. The charging circuit for capacitor 89 furtherincludes a current limiting resistor H3 and a contactor H4 of the relay93 in series across a current limiting resistor II5 of greater valuethan resistor II3 so that immediately upon reclosure of contactor I09(cessation of Welding current) the charging can proceed at a high rate.

Energizing coil I8 of relay I1 is arranged to be energized from line 24through a transformer I I5, conductor I I6, conductor II'I, switch 88,conductor H8, and a timer II9 which may be of the type which opens acircuit therethrough upon the expiration of a preselected period oftime. Swith 88 likewise controls the energization of coil 42 of relay Mfrom transformer I I5 through conductors I20, I2I, H8, and timer II9.Similarly switch 89 controls the actuation of relay 93 from transformerH5 through conductors I20, I22, I23, IIS, and timer IE9. Thus upon theapplication of proper welding pressure Welding current begins to flowand all the control circuits are .conditioned for operation.- Closure ofcontacto1s92 and 98 of relay 83'conditionsthe energizing circuit forsolenoid 88 as explained above 6; and the closure of contactor 92further condi tions a timing circuit, now to be described, the functionof which is to control the time of, energization of solenoid 88.

Aspace discharge device I I8 is connected across capacitor 89 throughlead 9I, contactor 92, conductor H1, and resistor I I8. The cathode andcontrol grid of tube II8 are coupled by meansof resistor II9 so that thetube is normally at zero bias and begins to draw full currentimmediately upon closure of contactor 92 which occurs at the start ofthe flow of welding current. stantially the full voltage of thecapacitor 89 appears across the resistor II8. In parallel with resistorH8 and tube H8 is a grid controlled gaseous discharge device I25, thecircuit of the same being traceable from lead I I1, anode-cathode oftube I25, conductors I26, timing capacitor I28, a variable resistor I29,a movable tap I30, and the negative end of resistance I02 to theopposite terminal of capacitor 89. Tube Iisnormally held non-conductiveby the negative bias impressed through resistor I3I, which resistornormally carries no current and which is connected to the negative endof the resistor II8.

Conductor I I I which is connected to the positive side of the output ofrectifier I2 is connected directly to the cathode of tube H8 while thecontrol grid or grids of the tube is connected directly to the conductorI I2 which leads from the negative side of the rectifier output. Uponappearance of rectifier voltage in the leads I II and H2, conduction intube I58 isthus substantially diminished or cut ofi thereby dividing thevoltage of the capacitor 89 between resistors I I8 and I3I. The drop inresistor I3 I, being in opposition to the normal grid bias impressed onthe tube I25.initiates conduction in this tube and commences thecharging of timing capacitor I29 through the circuit above outlined. Bymeans of certain arrangements now to be explained conduction in tube 90is initiated upon the capacitor I28 attaining a predetermined charge,the time required to attain such charge being determined by the settingof the variable resistance I29. A source of grid biasing potential fortube 90 is provided by the rectifier I32 deriving energy fromtransformer I08 and impressing its output across a capacitance I 33 andthe resistance element of a potentiometer I3 3. The adjustable tap ofpotentiometer I34 is connected to the control grid dined above.

of tube 90 through grid resistor I and the grid return circuit may betraced through potentiometer I34, conductor I21, resistor I29, conductorI28, a resistor I38, conductor I31, potentiometer I02, and conductor 99to the cathode of the discharge device 99. Upon the capacitor-I28attaining apreselected charge and a consequent development of.suflicient potential across resistors I38and I29 which is in oppositionto the normalnegative bias impressed on device conduction is initiatedin the discharge device 90 to dump, the energy from capacitor 89 intothe coil 86 through the energizing circuit therefor out- In this mannersolenoid 88 is furnished with sufiicient energy to properly actuate therelief valve-85 at the expiration of an accurately measured intervalfollowing the initiation of flow of Welding current to the electrodes I3and I4. A normally closed contactor I38 on relay 93 effects the completedischarge of the timing capacitor I28 between successive weldingoperations.

It should beunderstood that a control system of the nature describedabove is normally utilized Thus sub-.

in a complete welding machine having appropriate circuits and devicesfor effecting continuous automatic operation of the same. For example,such machine may, following the teachings of the prior art, includemeans to periodically actuate valve 81 and further means operable intimed sequence following actuation of valve 81 to turn or raise thepiston in cylinder 84 to open the electrodes and the switch 83 followingthe completion of a welding operation. The circuits of the controlsystem are then restored to their conditions indicated in the drawing inpreparation for the next succeeding welding cycle.

It should now be apparent that I have provided an improved electricresistance welding system and improved circuits having especial utilityin connection with such systems which accomplish the objects initiallyset out. The invention provides a simplified and wholly practicalarrangement for controlling the fiow of energy from a multiple phasealternating current source to a direct current load including thefurther modification of the control in accordance with variations in thevoltage of the source. The invention also provides an entirely practicaland accurate circuit for effecting the timed application of a change ina critical welding condition during a welding cycle as explained aboveand, moreover, teaches how such a circuit may be advantageouslyincorporated in a direct current resistance welding system.

The above specifically described embodiment of the invention should beconsidered as illustrative only as obviously many changes may be madetherein without departing from the spirit or scope of the invention. Forexample, insofar as certain obvious aspects of the system are concernedthe mechanical contactors l5 and I6 which control conduction in two ofthe current source conductors may, if desired, be replaced by suitableelectronic discharge devices connected back to back as will beunderstood. In this case the voltage compensation control feature of theinvention would be applied to each of the phases controlled byelectronic devices, it being observed that in accordance with statementsmade above the single voltage responsive circuit including the rectifier18 may be employed to vary the fixed direct current component of controlgrid bias of all the control devices. Reference should therefore be hadto the appended claims in determining the scope of the invention.

I claim:

1. In an electric resistance welding system having a welding transformerand a rectifier connected to the secondary thereof for supplyingunidirectional welding current, the combination of means to effectwelding pressure, means to vary the welding pressure during the weldingcycle, said last mentioned means comprising a solenoid and an energizingcircuit therefor, means comprising a timer to condition said energizingcircuit in timed sequence following the initiation of flow of Weldingcurrent, and means comprising a grid-controlled discharge device havingits control grid circuit connected across the output of said rectifierto initiate operation of said timer upon initiation of flow of weldingcurrent.

2. In an electric resistance welding system having a welding transformerand a rectifier connected to the secondary thereof for supplyingunidirectional welding current, the combination of means to effectwelding pressure, means comprising a solenoid and an energizing circuittherefor for varying the welding pressure during the welding cycle, saidenergizing circuit comprising a capacitor and a grid-controlled gaseousdischarge device in series therewith, a source of grid biasing potentialfor said device comprising a timing capacitor, a relay operative whenenergized to initiate a change in the charge on said timing capacitor,and means to energize said relay comprising a controlled dischargedevice having its control circuit connected across the output of saidrectifier.

3. In an electric resistance welding system having a welding transformerand a rectifier connected to the secondary thereof for supplyingunidirectional welding current, the combination of means to effectwelding pressure, means for varying the welding pressure during thewelding cycle, and means to control said means to vary comprising atiming device and means to initiate operation of said timing device uponthe appearance of voltage at the output of said rectifier.

4. In an electric resistance welding system having a welding transformerand a rectifier connected to the secondary thereof for supplyingunidirectional welding current, the combination of means to eifectwelding pressure, means for varying the welding pressure during thewelding cycle, a timing device, means operative upon said device timingout its period to operate said means to vary, and means to initiateoperation of said timing devicecomprising a controlled discharge devicehaving its control circuit connected across the output of saidrectifier.

5. In an electric resistance welding system having a source of weldingcurrent and means to connect said source to the welding load, thecombination of means to effect welding pressure, means for varying thewelding pressure during the welding cycle, a timing device, meansoperative upon said timing device timing out its period to actuate saidmeans for varying, and means to initiate operation of said timing devicecomprising a controlled discharge device having its control circuitconnected with means operative to supply a unidirectional potential uponactuation of said first mentioned means to connect.

6. In an electric resistance welding system having a welding transformerand a rectifier connected to the secondary thereof for supplyingunidirectional welding current, the combination of means to vary thequantity of energy translated from the alternating current source to theprimary of said welding transformer, means to vary the welding pressureduring the welding cycle, a timing device, means operative upon saidtiming device timing out its period to actuate said means to vary thewelding pressure, and means responsive to the appearance of potential atthe output of said rectifier to initiate operation of said timingdevice.

CLYDE E. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,175,841 Kafka et al Oct. 10,1939 2,221,576 Dawson Nov. 12, 1940 2,315,916 Whiteley et al. Apr. 6,1943 2,340,694 Rogers Feb. 1, 1944 2,356,859 Leathers et al Aug. 29,1944 2,477,211 Smith July 26, 1949

